1. Field of the Invention
The invention relates to a subscriber identity module (SIM) card, more particularly to a SIM card that employs a printed circuit board and that has RFID circuits implemented on board.
2. Description of the Related Art
In recent years, handset manufacturers have strived to provide handsets with mobile wallet functionality. For example, in the i-mode mobile wallet proposed by NTT Docomo of Japan, a FeliCa contactless integrated circuit chip is soldered onto a main board of an NTT third generation (3G) handset module to realize the mobile wallet function. Other methods can be used to build the function into the mobile phone, such as using the near field communication (NFC) integrated circuit chip offered by Philips, or the use of an infrared connection port, and have been proposed to achieve the same function. However, the above methods require customers to use new handsets, thereby resulting in lower consumer appeal.
Therefore, in view of practical considerations and to result in lower consumer costs, it has been proposed heretofore to integrate a mobile wallet module into a subscriber identity module (SIM) card, such as the second generation (2G) global system for mobile communication (GSM) SIM card or the 3G universal subscriber identity module (USIM) card. This approach only requires the user to change the SIM card and not the handset. Since the handset is provided with the mobile wallet function by simply installing a new SIM card, better consumer acceptance is possible.
Referring to FIGS. 1 and 2, a conventional SIM card 1 is shown to include a chip 119 mounted on or embedded in a polyvinyl chloride (PVC) plastic card 12. A surface of the plastic card 12 is provided with a metal foil 110 having eight contact pads 111-118 (C1-C8). The SIM card 1 is usually available in two sizes, i.e., an ISO-sized card and a plug-in sized card. The dimensions of an ISO-sized card are generally similar to those of credit cards. On the other hand, a plug-in sized card is generally 25 mm long, 15 mm wide and less than 0.9 mm thick.
When integrating the radio frequency identification (RFID) function of the mobile wallet module into a plug-in sized SIM card 1, there are several technical problems that should be addressed.
First, there is a need to provide an antenna on the SIM card 1. In view of the required length of the antenna, it is usually in the form of a looped or winding pattern. However, because of the small dimensions of the plug-in sized SIM card 1, not enough space is available to accommodate an effective RFID antenna. Therefore, to solve this problem, a coil antenna is installed on a back casing of the handset, and two antenna signal feed points on the handset main board are electrically connected to the C4 contact pad 114 and the C8 contact pad 118 of the SIM card 1. Alternatively, the coil antenna may be formed on a flexible printed circuit (FPC) board, and the FPC board antenna is subsequently connected to the SIM card 1. However, according to the ISO-7816-12 specification, the C4 contact pad 114 and the C8 contact pad 118 are allocated for electrical connection to a universal serial bus (USB) port. In addition, most handsets currently available on the market are not built with contacts for electrical connection with the C4 contact pad 114 and the C8 contact pad 118. As a result, connection of the antenna to the C4 contact pad 114 and the C8 contact pad 118 is impractical at this time. Furthermore, the conventional SIM card 1 with the PVC plastic card 12 is not suited for fixing a FPC board thereon. While it is possible to mount directly the FPC board on the C4 contact pad 114 and the C8 contact pad 118 at the top surface of the SIM card 1, the mounting process is prone to errors. In addition, when mounting the FPC boar don the SIM card 1, not only is it not possible to automate the mounting process, automated testing is not possible as well.